Psyche Mission Moved Up

byPaul GilsteronMay 25, 2017

Have a look at the design of the Psyche spacecraft now being built by Space Systems Loral in Palo Alto. What’s intriguing here is the five-panel x-shaped design of the solar array, reconfigured from a four-panel array on either side of the spacecraft. The juiced up array offers this asteroid-bound spacecraft higher power capabilities for its solar electric propulsion system, helping to support the recently adjusted higher velocity requirements of its journey.

Image: This artist’s-concept illustration depicts the spacecraft of NASA’s Psyche mission near the mission’s target, the metal asteroid Psyche. The artwork was created in May 2017 to show the five-panel solar arrays planned for the spacecraft. Credit: NASA/JPL-Caltech/Arizona State Univ./Space Systems Loral/Peter Rubin.

For the Psyche mission has been re-thought, with the interesting result that arrival at the unusual metal asteroid will take place a full four years earlier than the original timeline.

“We challenged the mission design team to explore if an earlier launch date could provide a more efficient trajectory to the asteroid Psyche, and they came through in a big way,” said Jim Green, director of the Planetary Science Division at NASA Headquarters in Washington. “This will enable us to fulfill our science objectives sooner and at a reduced cost.”

Expected to launch in 2023, the Psyche spacecraft will now launch in the summer of 2022, with arrival at Psyche, after a much faster journey, in 2026, four years ahead of the earlier schedule. The shortened travel time is all about trajectory, as Jim Green mentions above. The new plan calls for eliminating the Earth gravity assist, which dramatically shortens cruise time. The spacecraft also benefits from maintaining a greater distance from the Sun, reducing the need for heat protection. A Mars gravity assist is still planned for the mission in 2023.

A Discovery-class mission selected in 2017, the spacecraft is headed for one of the more exotic objects in the Solar System. The most massive M-type asteroid, 16 Psyche is thought to be made up of metallic iron and nickel, similar to the core of the Earth, rather than silicate rock or ice. About 200 kilometers in diameter, It is evidently the exposed core of a larger differentiated body that lost its rocky outer layers due to collisions in the distant past. The mission will study the asteroid’s geology, composition, magnetic field and mass distribution.

The Psyche team, led by Lindy Elkins-Tanton (Arizona State University) presented an overview of the mission at the 45th Lunar and Planetary Science Conference in 2014, seeing it as a journey back to the period of planetary accretion, when larger bodies had begun differentiating but were also being reshaped by collisions. And as the team points out, 16 Psyche gives us a way to see the interior of a rocky planet, the only way we can visit a metallic core. The team’s presentation included these key issues to address:

1. Is Psyche the stripped core of a differentiated planetesimal, or was it formed as an iron-rich body?

What were the building blocks of planets?

Did planetesimals that formed close to the Sun have very different bulk compositions?

2. If Psyche was stripped of its mantle, when and how did that occur?

3. If Psyche was once molten, did it solidify from the inside out, or the outside in?

4. Did Psyche produce a magnetic dynamo as it cooled?

5. What are the major alloying elements that coexist in the iron metal of the core?

6. What are the key characteristics of the geologic surface and global topography?

This is a new field: geology of metal objects.

Does Psyche look radically different from known stony and icy bodies?

7. How do craters on a metal body differ from those in rock or ice?

Seeking answers to these questions, the spacecraft will have an instrument payload that includes magnetometers, multi-spectral imagers, and a gamma ray and neutron spectrometer.

Image: Deep within the terrestrial planets, including Earth, scientists infer the presence of metallic cores, but these lie unreachably far below the planets’ rocky mantles and crusts. Because we cannot see or measure Earth’s core directly, asteroid Psyche offers a unique window into the violent history of collisions and accretion that created the terrestrial planets. Credit: University of Arizona.

For more, see Elkins-Tanton et al., “Journey to a Metal World: Concept for a Discovery Mission to Psyche,” available here. This JPL news release is also helpful.

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DJ KaplanMay 25, 2017, 12:27

Isn’t this Loral’s first science satellite in a long time? They normally make comsats.

Very much so. Over 200 if you believe their website. It’s actually their first exploration satellite that builds on the heritage ( and standard spacecraft bus ) of their successful geostationary comm satellites . In many ways revolutionary though as they will employ an established ” second generation ” 5 KW Hall ion thruster to help propel the craft through the cruise phase of the journey with an extra 20 % power provided by two 5 panel “X-wing” solar arrays rather than the originally intende ” straight fours” originally slated . These arrays can supply over 25 KW each via their state of the art DSS ( deployable space systems ) Rosa or mega- Rosa technology ( with solar concentrators) .

Compare that with chemically propelled Juno with just 14 KW from three solar arrays at start And just 434 W at Jupiter or the 2.3 KW powered NSTAR ion engine on prototype SEP powered Dawn.

Over 50 KW at mission start allows the Hall thrusters to operate at or near full power all the way out to Psyche ( circa 3 AU) even inverse square law allowing . In combination with an earlier more favourable launch trajectory have so reduced the transit time . The reduced xenon propellant requirement cf with chemical also allows more space for payload too. Dawn had the capacity to do more than one asteroid so it will be interesting if this becomes a secondary mission for far more capable Psyche too. Shorter journey time and SSL comm says have a lifetime of fifteen years . All things being equal I guess it will come down to cost and propellant margins .

More importantly still it shows the growing efficiency of soar power arrays . DSS arrays could already realistically produce near 400KW power at mission start . With increased radiation and cold resistance acquired through operations at radiation harsh geostationary orbits ( outer Van Allen belts and all) . Third generation arrays are rapidly gaining high technological readiness with DSS working on MegaRosaEx, a lightweight but rigid roll out array with around 40 % efficiency and potentially offering megawatts of power. NASA have already offered two 7KW as free technology for the New Frontiers 4 mission launching circa 2024 and in combination with these potent solar arrays could open up the outer solar system , with “SEP staging” reduced transit times and as with Psych making significant savings on operations costs in the process . Without the need of rare, expensive to purchase and handle radioisotope power sources . Imagine that if combined with one of the next generation of cost effective heavy launch vehicles . The future looks bright for planetary science even before the arrival of the more potent still 15 KW long life Hall thrusters Aerodyne are currently building for NASA under the experienced eye of the Glenn Research centre.

SSL and the JPL Psyche team worked together closely throughout the entire submission process. Exactly because SSL’s commsats with their high heritage 5KW SEP and durable spacecraft buses were easy to adapt for an asteroid intercept mission. SEP is still considered high risk for deep space use apparently , predominately because of the unpredictable effect this environment has on the photovoltaic cells of the solar arrays . Even now Psyche has been selected it is in a phase A development phase which will look to mature the technology further from its current TRL6/7. The use of “off the shelf” components works perfectly for the relatively narrow budgetary constraints of the Discovery programme. The foreshortened transfer to 16 Psyche and early launch date shave another crucial $100 plus off construction, development and operational costs . Money that can instead be used for better in situ science.

The good news is that SEP is viewed as offering a big role in future outer solar system New Frontiers missions , with JPL also leading the way. ( indeed rumour has it that three of the 12 New Frontiers 4 submissions target Saturn ) . The NEXT electric propulsion systems offered as “free” government technology for this programme were developed with Saturn “SEP staging ” ( SEP enhanced boosting part of the way to Saturn to reduce long transfer times) of spacecraft in mind and have suitable Technological readiness. It’s the large solar arrays necessary to power them , and their integration with the propulsion system that still needs work . Work which has already been done on a smaller scale with the SSL systems on Psyche and building up JPL’s knowledge base .( the Psyche SS.l spacecraft bus uses the same MegaRosa solar arrays proposed for integration with NEXT) JPL have at least one NF4 submission on the table .

What are the definitions of:
planetesimal
embryo
planet?
*************************
Their definitions can be somewhat “fluid,” depending on which expert is asked. There is also another term–“planemo”–that I’ve read about in this connection (I’m not sure what it means).

It’s just possible that Psyche, being a metal world, has jagged peaks like those that were (erroneously) depicted as being on the Moon (and which are depicted in the illustration above). Also, if Psyche is magnetized, it should be possible for an electromagnet-equipped spacecraft to “dock” on its surface and to accelerate away, all by changing the electromagnet’s polarity (these “tricks” would work best at either of Psyche’s poles, if it has a global magnetic field). If instead there are many local magnetic fields, as on the Moon, there should be numerous magnetic poles at which these things could be done.

It would be a safer place, too. If we saw Psyche’s albedo increase greatly over a short period of time, we’d know that the von Neumann “constructors” had gone berserk and turned its surface into shiny, “silver goo.” :-)

As principal investigator of the Psyche mission, Lindy Elkins-Tanton ’87, SM ’87, PhD ’02 is just the second woman to lead a NASA spacecraft mission to a planetary body. The first was her former MIT colleague, Vice President for Research Maria Zuber.

Alumna and former MIT professor Lindy Elkins-Tanton is working with MIT faculty in her role as principal investigator for NASA’s upcoming Psyche mission.

Psyche represents a compelling target for study because scientists theorize that it was an ordinary asteroid until violent collisions with other objects blasted away most of its outer rock, exposing its metallic core. This core, the first to be studied, could yield insights into the metal interior of rocky planets in the solar system.

“We have no idea what a metal body looks like. The one thing I can be sure of is that it will surprise us,” Elkins-Tanton says. “I love this stuff — there are new discoveries every day.”

NASA is preparing to travel to a world unlike any other it has visited before. The agency has sent spacecraft to terrestrial planets, gaseous planets, icy moons, and rocky asteroids. Now, following its approval as a Discovery mission in February of this year, a spacecraft set for launch in 2022 will visit the main-belt asteroid Psyche, a metal world that scientists believe is made almost entirely of nickel and iron.

The nickel-iron makeup of Psyche suggests that it may be the exposed core of an early protoplanet, torn apart by hit-and-run collisions during the early history of the Solar System.

“Psyche is a unique body because it is, by far, the largest metal asteroid out there; it’s about the size of Massachusetts,” said David Oh, the mission’s lead project systems engineer at the Jet Propulsion Laboratory (JPL) via a news release. “By exploring Psyche, we’ll learn about the formation of the planets, how planetary cores are formed and, just as important, we’ll be exploring a new type of world.”

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